With less than two weeks to go until Election Day, Democratic presidential candidate Barack Obama continued to focus on the domestic economy Tuesday, which public opinion polls show is the top issue in the campaign. But Obama's Republican opponent, John McCain, tried to shift the focus to foreign policy and national security issues. VOA National Correspondent Jim Malone reports from Washington.

With the latest national polls showing Obama leading McCain by an average of about seven points, Senator McCain is trying to shift the focus of the campaign debate away from the economy.

Biden told Democratic fundraisers that Obama would probably face an international crisis during his first six months in office.

"They are going to want to test him," he said. "And they are going to find out this guy has got steel in his spine."

McCain used Biden's remarks to raise questions about Barack Obama's experience and his readiness to handle foreign policy challenges president.

"We don't want a president who invites testing from the world at a time when our economy is in crisis and Americans are already fighting in two wars," he said. "What is even more troubling than that is that Senator Biden told campaign donors that when that crisis hits, they would have to stand with him because it wouldn't be apparent that Senator Obama would have the right response. Forget apparent. We know Senator Obama won't have the right response!"

Public opinion polls show voters are most concerned about the state of the U.S. economy, and that has put the McCain campaign on the defensive for the past several weeks.

During an interview with CBS television, McCain dismissed the notion that the state of the economy was a losing issue for his campaign.

"That is simply not true. That is simply not true," he said. "We have been focusing on the economy. Listen to me. I'm the candidate. And this campaign is about the economy."

For his part, Senator Obama remained focused on the economy and its impact on average Americans.

Obama convened what he described as a "jobs summit" in Florida that included the Democratic governors of Michigan, New Mexico and Ohio.

"We have had an eight-year experiment and we've seen where it leads," he said. "This economic crisis is the final verdict on that failed leadership. It is time to try something new."

Passions are running high in both political camps in the final days of this extraordinarily long presidential campaign.

At one point, Obama tried to calm the crowd after it erupted in boos at the mention of Senator McCain.

"Senator McCain back in January insisted that the fundamentals of the economy were strong. [Boos from audience] No, no. We don't need that," he said. "We just need you to vote."

Most analysts say the economy has become the driving force in the campaign and is responsible for Obama's lead in public opinion polls.

McCain has tried to change the subject at various times to Obama's tax proposals, his relative lack of experience in government and his past association with 1960s radical William Ayers.

But University of Virginia expert Larry Sabato says McCain is finding it difficult to shift the focus away from the economy.

"The economic crisis has become the black hole of the 2008 campaign," he said. "McCain is trying to change the subject and he is using all the materials at his disposal. But probably this is not going to work."

Obama will take a break from the campaign trail later this week to visit his ailing grandmother in Hawaii. His 85-year-old grandmother, Madelyn Dunham, helped raise Obama and has long been a central figure in his life.